Air lock for a sifter



Aug. 27,1940.

E. G. BERRY AIR LOCK FOR A SIF'IER Filed Dec. 20, 1937 llw' VE T" EUGENEG. BERRY Patented Aug. 27, 1940 STTES AIR LOCK FOR A SKFTER noisApplication December 20, 1937, Serial No. liiilfi'ilz ll Claim.

This invention relates to an air lock primarily designed for use inconnection with sifters but adapted for other uses.

In sifting flour and the like material, it is common practice to use asifter box having several sieves covered with bolting cloth thereinthrough which the flour passes. boxes are provided with dischargeopenings through which the sifted material passes.

It has been discovered that air currents enter through the dischargeopenings and strike or exert pressure against the bottom of the boltingcloth with the result that the sifting of material through said cloth ismaterially retarded.

It furtherappears that this condition has prevailed ever since suchsifters were used without anyone discovering that the sifting efliciencyof the bolting cloth was materially reduced through the backing upeffect of the air currents.

In the sifting of material used in food products, it is highly essentialto keep the same pure and clear of foreign matter such as metal or thelike. For this reason it is desirable that an air lock be constructedwithout the use of springs or such parts as might break or chip and findtheir way into the sifted material.

It is therefore an object of this invention to provide a simple form ofair lock that is free of springs, hinge joints and such parts as mightbreaker chip off and find their way into the sifter material.

The invention comprises the novel structure and combination of partshereinafter'described and more particularly pointed out and defined inthe appended claim.

In the accompanying drawing which illustrates a preferred form of thisinvention and in which similar reference numerals refer to similarfeatures in the different views:

Figure 1 is an elevational View of an air lock embodying this inventionwith a part broken away.

Figure 2.is a top plan view of the structure shown in Figure 1.

In the drawing which illustrates one embodiment that this invention mayassume, there is shown a substantially square sheet metal chute member Ihaving a surrounding flange 2 upon its upper edge. The flange 2 isadapted for attachment to the bottom of a sitter box, parts of which areindicated at 3, such as is shown in the Reimuler and Berry applicationSerial No. 131,821 filed March 19, 1937. For the purpose of illustratingone way in which the flange 2 may be secured to the sifter box,apertures 4 are These sifter shown in the flange 2 for receiving screwsor bolts or the like.

The chute member 5 is provided with a bottom ring plate ii which may besoldered thereto. This plate 5 is provided with a circular aperture 6that corresponds with the diameter of a cylindrical collar l which has aflange soldered to the bottom plate so that the opening in the collarwill r gister with said aperture. This collar is provided with a bead 8at its lower end and forms a support for a stocking leg clamp (notshown).

Against the upper part of the rear wall of the chute l and within suchchute there is secured an angle member 8. This angle member is securedby soldering one flange to the rear Wall of the chute with the otherflange to extending inwardly as shown in Figure 1.

A valve flap 5 made of spring tempered phosphorus bronze about .005 ofan inch thick has its rear edge soldered to the lower side of the flange8a and additionally secured by rivets Hi. This flap fits freely withinthe mouth of the chute I so it can readily flex downwardly as shown indotted lines in Figure 1 when material from the sifter box strikes thesame in sufficient volume. The vibration of the sifter box materiallyaids this downward flexing movement.

It has been discovered that when a thin sheet of phosphorus bronze isspring tempered it acquires a high degree of elasticity that causes itto readily spring to a horizontal position or to right itself after aflexing operation. It has been further discovered that when such a valveflap is attached close to the sifter box that the vibrations arisingfrom the operation of the box will materially aid and induce a downwardflexing movement of the valve flap.

Upon the interior front wall of the chute I, there is secured a secondangle l l having its outstanding fiange lla overlap the forward marginor edge of the flap 9.

Along the interior sides of the chute l are soldered small angle membersl2, the outstanding flanges of which overlap the top side edges ormargins of the flap 9. Thus there is an overlapping lip or narrow flangeupon the front and side margins of the flap valve ii that limits itsupward movement when the same springs back from its dotted line positionshown in Figure 1.

The valve flap 9 is extremely flexible or resilient and does not requiremuch force to flex the same downwardly as shown in dotted lines inFigure 1 for the passage of sifted material between its front edge 9aand the adjacent wall of the chute especially when it is vibrated. The

sifted material in passing through this space will be more or lessconcentrated or compacted and will prevent incoming currents of air.

It might be mentioned that the sifted material that may drop upon thecorners of the bottom plate 5 will be soon shaken off through thevibrations of the sifter.

Thus the valve fiap 9 will permit the discharge of material but willprevent incoming currents of air that have heretofore retarded thesifting of material through the bolting cloth.

Due to the fact that this valve flap is not hinged nor controlled bysprings there is no part that can break and produce particles that willfind their way into the sifted material.

It will be appreciated that in using a substantially square orrectangular chute member, it is possible to secure the valve flap alongone entire margin so that it can be firmly supported, a fea-. ture thatwould not be possible if a cylindrical chute member were used. It willfurther be appreciated that the use of a thin phosphorus bronze valvefiap that is spring tempered and subjected to the vibrations arisingfrom a sitter box will readily accomplish the purpose desired.

From the foregoing, it will be apparent that a very simple and novelflap valve has been invented that is especially adapted as an air lockfor sifters to prevent air currents from entering and retarding thepassage of material through the bolting cloth.

I am aware that many changes may be made and numerous details ofconstruction may be varied through a Wide range without departing fromthe principles of this invention, and I therefore do not purposelimiting the patent granted hereon otherwise than necessitated by theprior art.

I claim as my invention:

The combination with a vibratory sifter having a movable frame definingan outlet opening for material, an air lock comprising a chute having arectangular upper portion, an outwardly extending peripheral flange atthe top of the chute for attaching it in suspended position to the framearound the outlet opening, a thin, flexible, rectangular metallic flapextending into the chute, and members respectively disposed at oppositetop edges of the chute forming inwardly directed flanges lyingsubstantially in a plane perpendicular to the chute axis, said flapbeing rigidly secured at one end to one of said flanges and having itsfree end extending under the other of said flanges, the latter flangeacting to restrain the flap against upward flexing movement, butenabling downward flexing movement thereof under weight of material fromthe outlet opening.

EUGENE G. BERRY.

